Apart from the capacity maximization, the design goal for joint precoding can be different. Specifically, to reduce the power consumption, some researchers have proposed the methods to minimize the transmit power subject to the constraints of the user requirements [1]}, and the authors in [2]} have developed a method to maximize the energy efficiency. Some researchers have considered the fairness among users, and some methods have been proposed to maximize the minimum sinr [3]}, [4]}. In addition, minimizing the ser was considered in [5]}.
